1. Field of the Invention
Embodiments of the present invention pertain to a cooling apparatus, and more particularly, but not by way of limitation, to cooling systems incorporating toroidally shaped, low-profile extrusions (LPEs).
2. History of Related Art
As is explained in greater detail hereinbelow, LPE cooling devices are extremely useful in printed circuit board (PCB) level cooling of electronic components, and for use as heat exchangers in applications where space is limited and/or low weight is critical.
LPE refers to a heat exchange apparatus including an integral piece of metal having a series of micro extruded hollow tubes formed therein for containing a fluid. LPEs preferably have multi-void extruded tubes (micro-tubes) designed to operate under the pressures and temperatures required by modern environmentally safe refrigeration gases and to resist corrosion. Aspects of the LPE application to the present invention are set forth and shown in co-pending U.S. patent application Ser. No. 09/328,183 and Ser. No. 10/305,662 assigned to the assignee of the present invention and incorporated herein by reference.
LPEs can currently be manufactured with a profile, or height, as low as about 0.05 inches and with tubes of varying inner diameters. Of course, future advances may allow such low-profile extrusions to be manufactured with an even smaller profile. Such low-profile extrusions have been conventionally used in heat exchanger applications in the automotive industry, and are commercially available in strip form (having a generally rectangular geometry) or coil form (a continuous strip coiled for efficient transport).
An example of a low-profile extrusion is described in a brochure entitled “Thermalex, Inc.—Setting A Higher Standard in Aluminum Extrusions” (hereinafter the “Thermalex Brochure”). The Thermalex Brochure provides additional detail regarding the Thermalex LPEs and is incorporated herein by reference.
U.S. Pat. No. 5,342,189 to Inamura, et al, which is incorporated herein by reference, provides additional detail regarding an extrusion die for making such LPEs. The extrusion die is used for making multi-cavity flat aluminum tubes, which are used for small heat exchanger components, in automotive air-conditioners, condensers, and radiators. The insert die is composed of a male die section having a protrusion part and a female die section, having a die cavity, and is held detachably in a die holder. The male section is a roughly rectangular plate-shaped component, and has an integrally formed twist prevention region which is inserted into the receiver groove of the female section which is integrally formed on the female section. The protrusion part defines the cavity shape of the multi-cavity flat tube, and the female section has the die cavity of the required cross sectional shape to define the outer shape of the tube.
U.S. Pat. No. 5,353,639 to Brookins, et al, which is incorporated herein by reference, provides additional detail regarding a method and apparatus for sizing a plurality of micro-extruded tubes used in such LPEs. As described by the Brookins patent, a predetermined number of micro-extruded tubes are stacked on the base fence between the fixed side fence and the clamping fence. The internal webs of the tubes are aligned throughout the stack, perpendicular to the plane of the base fence. The clamping fence is moved toward the stack of tubes to prevent the stack from moving laterally. The die platen is moved toward the stack of tubes and the mating surface of the die platen is in mating engagement with a side surface of the uppermost tube in the stack. A predetermined amount of pressure is applied to the stack of tubes through the die platen. The pressure is applied equally across the entire side surface of the uppermost tube and is transmitted equally through all the tubes of the stack in the sizing die.
Other developments in cooling apparatus may be seen in U.S. Pat. No. 5,285,347 to Fox et al., which describes a hybrid cooling system for electrical components. A hybrid heat sink is specially adapted to transfer heat to two heat transfer fluids. The heat sink is incorporated into a cooling system in which some of the electronic components of an electronic device may be cooled by two heat transfer fluids and some electronic components may be cooled by one heat transfer fluid. The electronic components are mounted on a circuit board. In the Fox reference, one of the heat transfer fluids is air and one is a liquid. The hybrid heat sink is attached to electronic components that cannot be cooled to the normal operating range by the cooling air alone. The cooling air is caused to flow over the surface of the heat sink, removing some of the heat. In addition, the liquid heat transfer fluid is caused to flow through the heat sink, thereby removing additional heat.
In addition, U.S. Pat. No. 5,901,037 to Hamilton, et al. describes a system for closed loop liquid cooling for semiconductor RF amplifier modules. The system includes a combination of a plurality of elongated micro-channels connected between a pair of coolant manifolds for conducting liquid coolant beneath the transistors to dissipate the heat generated by the transistors. The system also includes a heat exchanger, a miniature circulating pump located on the module, and passive check valves having tapered passages for controlling the flow of coolant in the loop. The valve includes a truncated pyramid-shaped micro-channel valve having no moving parts and is fabricated so as to be a part of either the circulating pump assembly, the coolant manifold, or the micro-channels.
It has been shown that the use of low-profile heat pipes greatly improves the efficiency of the heat removal process, while making the cooling package lightweight and compact. It is shown in co-pending U.S. patent application Ser. No. 09/328,183, Ser. No. 10/328,438, Ser. No. 10/328,537, Ser. No. 10/335,373 and Ser. No. 10/345,475 that heat pipes of the unstacked variety provide superior performance in a low-profile, light weight package.
Embodiments of the present invention provide a cooling element utilizing a heat pipe with a toroidal shape. The toroidal shape allows the heat pipe to remove heat from a heat generating element while exhibiting a small footprint. The toroidal heat pipe is useful in environments having little space but requiring efficient heat removal.